Author Topic: DMM says 0.3 VAC instead of 3.0 VAC

November 10, 2021, 10:41:22 PM
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herrturtur

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Here is where I am: Setup Channel 1, Step 6.

Signalflow: line level XLR from my USB Audio interface > into Monitor Controller > into Heritage Audio OST-4 V2 lunchbox > CP4500 connected via XT500 extension.

Doublechecked the CP4500:
Threshold +15
Makeup 0
Mix 100%

From Pro Tools Signal Generator, I am already sending 0dBFS and a fair amount of gain through my Monitor Controller into the lunchbox > CP4500. Can't get the DMM say 3.0 VAC staying within reasonable output gain of the monitor controller. DMM reads 0.3 VAC. Trimmers + Threshold + Makeup Gain work as expected.

I am new to DIY (and admittedly, using a DMM as well) - so just to doublecheck: The DMM should be connected to pins 2 (+) and 3 (-) of the XT500 (TP positions "2" and "4") / respectively of the XLR output pins of the Lunchbox..? I tried each combination, but no 3.0 VAC with makeup gain at 0.

Not sure If i can proceed to the next PCB like this :(

Thanks in advance!

PS: in case the pictures below show as gigantic as on my screen, with shift + mousewheel I am able to scroll right where you can see the pins etc.




« Last Edit: November 11, 2021, 09:19:30 AM by herrturtur »

November 11, 2021, 11:34:08 AM
Reply #1

herrturtur

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really strange: I went through the testing procedure "In case your CP4500 doesn't work as expected".. and everything was fine (except for the voltage not reading 3.0VAC, no matter how hard I cranked the output of my interface). Since I am not in the studio building the compressor, I use my home desktop USB interface which is a Roland Rubix22.

I then threw an Apogee Groove Dongle USB Interface at my mac and all of a sudden I get 3.0 VAC. I wonder if the interface is really suffering from output power or if there could be another reason for not getting enough volts...? So far so good. I will proceed with the setup guide :)

Cheers!

November 11, 2021, 03:48:50 PM
Reply #2

JPK

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The specs of the Rubix22 say 8dBu maximum output. This is 1.95VAC at 0dBFS.
So it is not surprising that you could not reach the 3V.
JPK

November 15, 2021, 10:33:24 AM
Reply #3

herrturtur

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Thanks for maintaining the forum so well! I did not expect the rubix to be that "weak". Completely assembled the CP4500 and tested in the studio, I am really happy with it! Cheers :)